Ehrenberg studied at the University of Berlin (M.D., 1818) and was associated with the university throughout his career. He took part in a scientific expedition (1820–25) to Egypt, Libya, the Sudan, and the Red Sea under the auspices of the university and the Prussian Academy of Sciences. The expedition’s only survivor, he collected about 34,000 animal and 46,000 plant specimens. With German explorer and naturalist Alexander von Humboldt, he participated in 1829 in an expedition, sponsored by Tsar Nicholas I of Russia, to Central Asia and Siberia.

Ehrenberg identified and classified a number of terrestrial and marine plants, animals, and microorganisms collected on expeditions. He proved that fungi come from spores and demonstrated the sexual reproduction of molds and mushrooms. He was the first to study in detail the anatomy, habits, and life history of coral, and he identified planktonic microorganisms as the cause of bioluminescence in the sea. Ehrenberg discovered the microscopic fossil organism content of various geologic formations and noted that certain rock layers are composed of such single-cell fossils.

Ehrenberg advanced the view that all animals, from the most minute to the largest, possess complete organ systems, such as muscles, sex organs, and stomachs; he believed his concept of “complete organisms” (later refuted by French biologist Félix Dujardin) disproved both the theory of spontaneous generation and the validity of the traditional arrangement of animals in a simple-to-complex series. Arguing that a single “ideal type” may be applied to all animals, he worked toward a comprehensive system of classification, in which he used social behaviour as an important criterion, but he placed humans apart from other animals on the basis of intelligence.

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